The present invention generally relates to a system and method for increasing the efficiency of a system by running parallel algorithms or cipher operations. More particularly, this inventions relates to a system for passing incoming frame data to two or more algorithms, cipher or message integrity check operations in parallel and determining which one is the correct result.
Modern wireless networks (WLANs) require robust and flexible security. Three aspects of current WLANs make it particularly difficult to implement quality security as compared to the equivalent wired local area network (LAN). First, the WLANs are open in nature with transmission through the air and therefore lack the same physical barriers found in LANs. Second, WLAN end user units are mobile and roam from access point (AP) to AP so crypto keys, encryption parameters and encryption state must be timely updated. Third, a central processing unit (CPU) must often be used to determine the crypto and authentication algorithms to be run before any crypto operation can begin.
Because WLANs lack the same physical barriers as in wire LANs, intruder detection is more difficult. To help defend a WLAN from intrusion, a form of authentication is used to be sure the client requesting use of the LAN is an authorized user. In the 802.11 WLAN environment, the IEEE specification 802.11i uses a message integrity check (MIC) with a key. The IEEE 802.11i standard requires the keys to be periodically changed. Referring to FIG. 1, the key update typically starts when an AP 10 request an updated key from the authentication, authorization, and accounting (AAA) server 12. Ideally, the new key will be used in place of the old key from as soon as the AAA server creates the new key. However, because one AP may service many roaming clients 14, they are not all updated with the new key at the same time. Also, the AP needs to update its own packets for transmission and this takes some time.
FIG. 2 is a hardware block diagram that depicts more precisely how both old and new keys can still be valid in a wireless system 200. Frames enter the wireless network from the wired network through a network interface 210. Usually they are buffered into a memory 220 until a host processor 230 has time to process them and figure out what security algorithms and keys are needed for each packets encryption, decryption, or MIC authentication. The host processor 230 will often need to look up a particular packet's key, and cryptography settings in another table in order to know how to process a particular packet. However, once the packet is waiting in the queue, the AAA server may change the key value (or other security values) resulting in an old key and a new key. Once the host processor 230 detects the security algorithm change or key change, it begins to use the new algorithm or key. The result is that the memory 240 queue ends up with some frames ready to transmit with the old key and some keys ready to transmit with a the new key.
Adding MIC checks to the packet frames is currently done in software running on the AP host CPU. The host then sends the frames with the added MIC down to the radio where they are later queued for transmission. Once queued, it is too late to change the frames on the radio, so they will be sent with the MIC calculated with the old key. The situation is symmetrical on frames received by the AP from the clients. The clients will also have frames queued with MICs calculated with old keys until it has had time to updated the start using the new key. Therefore, the AP will continue to get frames that were authenticated with the old key for some period of time after a key update.
From a security perspective, there is no real problem since it is a natural affect of the asynchronous nature of the key update. It is still safe to send transmit (TX) and receive (RX) frame using the old key for a short period of time without compromising the WLAN.
The asynchronous update of the keys reduces the quality of service (QOS). Past attempts to solve this problem address how the key is updated but fail to account for the reduction in QOS. The frames failing the MIC check may be completely dropped. The frames can be resent later after the receiver sends a NACK or other alternative indication that the frame was invalid. Alternatively, the MIC check can be performed first with the new key and if that fails the MIC check then the check can be performed with the old key but this requires double the valuable CPU time because the frame and key both need reloaded and then the entire calculation must be recalculated with the new key. In both of these solutions QOS suffers because dropping frames or spending more time than needed running frames through a double MIC check with each key creates latency as to when the frames finally are ready to be processed after authentication. This additional latency can cause adverse user affects when the frames are used in QOS intense applications such as streaming video or voice over IP (VoIP) audio.
The exact security algorithm implemented in a frame can depend on a client address, quality of service (QOS) specification for that client, and the security association. Additionally, different basic service set identifiers (BSSIDs) often require different security protocols for groups of nodes in the same BSSID. Resolving this information to determine which security algorithms to use takes some time and creates setup lag. The setup lag may even contribute to a dropped packet or memory bottleneck if the input arrival rate is fast and the CPU cannot select and set up the proper security algorithm in time for an RX overrun.
This invention solves the problem increased latency because of key updates and determining the correct security algorithm as well as other problems encountered in the prior art. This invention provides a system and method to increase system throughput when computing MIC and other cipher operations.